Datasheet

236
7728G–AVR–06/10
ATtiny87/ATtiny167
21.7.9 Programming the Fuse High Bits
The algorithm for programming the Fuse High bits is as follows (refer to “Programming the
Flash” on page 232 for details on Command and Data loading):
1. A: Load Command
“0100 0000
b
”.
2. C: Load Data Low
Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit.
3. Set BS1 to “1” and BS2 to “0”. This selects high data byte.
4. Give WR
a negative pulse and wait for RDY/BSY to go high.
5. Set BS1 to “0”. This selects low data byte.
21.7.10 Programming the Extended Fuse Bits
The algorithm for programming the Extended Fuse bits is as follows (refer to “Programming
the Flash” on page 232 for details on Command and Data loading):
1. A: Load Command
“0100 0000
b
”.
2. C: Load Data Low
Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit.
3. Set BS1 to “0” and BS2 to “1”. This selects extended data byte.
4. Give WR
a negative pulse and wait for RDY/BSY to go high.
5. Set BS2 to “0”. This selects low data byte.
Figure 21-5. Programming the FUSES Waveforms
21.7.11 Programming the Lock Bits
The algorithm for programming the Lock bits is as follows (refer to “Programming the Flash” on
page 232 for details on Command and Data loading):
1. A: Load Command
“0010 0000
b
”.
2. C: Load Data Low
Byte. Bit n = “0” programs the Lock bit. If LB mode 3 is pro-
grammed (LB1 and LB2 is programmed), it is not possible to re-program the Lock bits
by any External Programming mode.
3. Give WR
a negative pulse and wait for RDY/BSY to go high.
4. The Lock bits can only be cleared by executing Chip Erase.
0x40 DATA XX
DATA
XA1 / BS2
XA0
PAGEL / BS1
AC
0x40 DATA XX
AC
Write Fuse Low byte Write Fuse high byte
0x40 DATA XX
AC
Write Extended Fuse byte
RDY/BSY
WR
OE
RESET +12V
XTAL1